Diffuse soil gas emission measurements on the volcanic island of Saba, Lesser Antilles

Abstract Monitoring changes of geochemical parameters in the subsurface around volcanoes is crucial for hazard assessment and early warning. This study establishes a baseline of soil CO $$_2$$ emission from its flanks of the Mount Scenery stratovolcano, on Saba in the Caribbean Netherlands, during its period of quiescence. The soil CO $$_2$$ flux and carbon isotope variation were mapped across the island to find patterns and locations of higher flux. Additionally, soil gas was analyzed for helium isotopes at ‘Green Gut’, a location which has an anomalous soil temperature. Results reveal spatial variations in temperature and soil CO $$_2$$ fluxes across the island, with higher temperature and fluxes observed along a transect from the southwest to the island’s north side. The anomalous sites identified from soil CO $$_2$$ flux and carbon isotopes measurements align with known alteration and temperature anomalies, including an abandoned mine in The Bottom and cracks along the road in ‘Green Gut’. The identified transect partially overlaps with a previously proposed ancient sector collapse, but our results suggest an extension northward. Integrated soil CO $$_2$$ flux and carbon isotope data across the island indicate that the emitted gas is a mixture of biogenic, atmospheric, and hydrothermal-magmatic sources.